Ceramic compositions having high dielectric constant and high specific resistivity

ABSTRACT

The ceramic composition comprises lead magnesium tungstate [Pb(Mg1/2 W1/2)O 3  ], lead titanate [PbTiO 3  ] and lead nickel niobate [Pb(Ni1/3 Nb2/3)O 3  ]. When the ternary composition is expressed by [Pb(Mg1/2 W1/2)O 3  ]x [PbTiO 3  ]y [Pb(Ni1/3Nb2/3)O 3  ]z where x+y+z=1.00, it lies on lines interconnecting five points (x=0.693, y=0.297, z=0.01), (x=0.495, y=0.495, z=0.01), (x=0.195, y=0.465, z=0.35), (x=0.10, y=0.40, z=0.50) and (x=0.06, y=0.24, z=0.70) and in a region bonded by the lines. In modifications, for the purpose of improving the mechanical strength, 0.02 to 3 mol % of at least one auxiliary ingredient selected from the group consisting of Nb, Ta and Sb, 0.05 to 8 mol % of [Pb(Mn1/3 Ta2/3)O 3  ] 0.05 to 10 mol % of [Pb(Mn1/3 Nb2/3)O 3  ] or 0.05 to 6 mol % of [Pb(Mn1/3 Sb2/3)O 3  ] is added.

BACKGROUND OF THE INVENTION

This invention relate to a ceramic composition, especially suitable for use as a dielectric material for fabricating a laminated capacitor, having a high dielectric constant, a high specific resistivity at temperatures of 20° C. and 125° C., a high mechanical strength and capability of being sintered at a temperature of from 900° to 1050° C.

When manufacturing a practical laminated capacitor by using a ceramic composition, as its electric characteristics, such factors as dielectric constant, percentage of variation thereof due to temperature variation, specific resistivity, dielectric loss, and DC bias dependency, etc. must be evaluated. More particularly, the dielectric constant and the specific resistivity must be high as far as possible, whereas the percentage of variation of the dielectric constant due to temperature variation, dielectric loss and variation in the dielectric constant caused by the DC bias must be small as far as possible. Regarding the specific resistivity, according to EIA specification Class II, it is specified that the insulating resistance should be higher than 7,500 Meg ohms or the product of resistance and capacitance (RC product) should be higher than 75 ohm F(=75 meg ohm·μF).

More particularly, unless the product of the dielectric constant and specific resistivity of a ceramic composition is larger than a predetermined absolute value, it is impossible to manufacture a capacitor having any capacitance, especially a large capacitance, and satisfying a practical regulation. Accordingly, the field of use of a ceramic composition not satisfying this condition is greatly limited. In an ordinary laminated capacitor, (n+1) internal electrodes and n (where n is a positive integer) capacitor layers having the same thickness are alternately laminated. Denoting the capacitance of each layer by Co, and the insulating resistance thereof by Ro, the capacitance C of the laminated capacitor becomes nCo, while insulating resistance R becomes Ro/n. Denoting the dielectric constant of the ceramic composition by ε, the dielectric constant of vacuum by εo, the specific resistivity of the ceramic composition by ρ, the thickness of each layer by d, and the overlapping electrode area by S, the capacitance Co of a single layer capacitor becomes εoεS/d, and Ro becomes ρd/S. Consequently, the product C×R of the capacitance C of an n-layer laminated capacitor and the insulating resistance R is expressed by an equation,

    (ρD/nS)×(nεoεS/d)=εoερ.

Thus, the CR of the laminated capacitor having any capacitance becomes constant or normalized, i.e., εoερ.

A requirement that RC is to be higher than 75 ohm F can be fullfilled when RC=εoερ=8.855×10⁻¹⁴ (F/cm)×ε×ρ≧75 ohm·F and accordingly, when ερ≧8.47×10¹⁴ ohm·cm. For example where ε=5000, a relation ρ≧1.69×10¹¹ ohm·cm is required, and where ε=10,000, a relation ρ≧8.47×10¹⁰ ohm·cm is required. With any large capacitance, laminated capacitors formed of ceramic compositions having a value of ρ larger than these values in accordance with the dielectric constant can satisfy a condition RC≧75 ohm·F. Where ε is 5,000 and ρ is less than 1.69×10¹¹ ohm·cm, to obtain an insulating resistance higher than 7500 meg·ohm, the upper limit of the capacitance would be 0.01 μF. As a consequence, with a ceramic composition having a low specific resistivity, it is impossible to obtain a laminated capacitor having a small size and a large capacity, the features of the laminated capacitor.

Where a stringent reliability is required, the BX characteristic defined by U.S. Military Specification (MIL), for example, requires an insulating resistance of more than 100,000 meg·ohm at 25° C. or a product RC of more than 1000 meg·ohm·μF. It is also defined that at 125° C. the insulating resistance should be 10000 meg·ohm or more or the product RC should be 100 meg·ohm·μF or more.

A high insulating resistance, or a small leakage current not only at room temperature but also at a high temperature, ensures that dielectric breakdown caused by thermal runaway due to an increased leakage current can be prevented and that the reliability of the capacitor can be improved.

In a laminated chip capacitor wherein the layers of the chip capacitor are soldered on a substrate, owing to the difference in their thermal expansion coefficients, the chip is subjected to a mechanical stress and tends to be cracked or damaged. In the case of a dip capacitor encapusulated in an epoxy resin casing or the like, the dip capacitor sometimes cracks due to stress applied by the encapusulation. In any case, where the ceramic composition comprising the laminated capacitor has a low bend strength, the tendency to cracking and breakage increases, thus decreasing reliability. For this reason, it is practically important to increase as far as possible the bend strength of the ceramic composition.

In addition, the internal electrodes utilized in laminated capacitors is required to have a melting point higher than the sintering temperature of the ceramic composition. For this reason, in order to make possible to use inexpensive Ag (silver) electrodes, it has been necessary to decrease as far as possible the sintering temperature. Accordingly, development of a new material that can substitute for BaTiO₃ system ceramic sintered at a temperature of from 1300° to 1400° C. has been desired. For example, U.S. Pat. No. 4,048,546 to R. J. Bouchard et al discloses a Sr_(x) Pb_(1-x) TiO₃ -Pb(Mg_(1/2) W_(1/2))O₃ type ceramic. In this reference, ε is at most 8050 but nothing is taught about the specific resistivity and the mechanical characteristics of the ceramic. Japanese Preliminary Patent Publication No. 111011/1980 by Fujiwara et al discloses Pb(Mg_(1/3) Nb_(2/3))O₃ -PbTiO₃ -Pb(Mg_(1/2) W_(1/2))O₃ type ceramic. This reference does not at all teach the specific resistivity and the mechanical characteristics. Japanese Preliminary Patent Publication No. 144610/1980 by Fujiwara et al teaches addition of Pb(Mn_(1/2) W_(1/2))O₃ to Pb(Mg_(1/3) Nb_(2/3))O₃ -PbTiO₃ -Pb(Mg_(1/2) W_(1/2))O₃ for the purpose of improving the insulating resistance. As a reference, in Table 1 of this publication is shown the insulating resistance of a ternary composition Pb(Mg_(1/3) Nb_(2/3))O₃ -PbTiO₃ - Pb(Mg_(1/2) W_(1/2))O₃. Although the insulating resistance is not converted into specific resistivity, a material constant, the specific resistivity can be expressed as follows on the assumption that the percentage of shrinkage is 15% (an ordinary value) and by taking into consideration dimensions after molding. Then the insulating resistance 7×10⁹ ohms of the composition No. 6 [Pb(Mg_(1/3) Nb_(2/3))₀.45 Ti₀.25 (Mg_(1/2) W_(1/2))₀.30 O₃ ] shown in the table 1 is shown by 2.1× 10¹¹ ohm·cm in terms of the specific resistivity. Consequently,

    εεoρ=108 meg·ohm·μF, where ε=5760.

In the same manner, the insulating resistance, 8×10⁹ ohm, of sample No. 11 having a composition [Pb(Mg_(1/3) Nb_(2/3))₀.15 Ti₀.30 (Mg_(1/2) W_(1/2))₀.55 O₃ ] is shown by 2.4×10¹¹ ohm·cm in terms of the specific resistivity. Thus, εεoρ=98 meg·ohm·μF (where ε=4560). The insulating resistance, 2×10¹⁰ ohm, of sample No. 16 having a composition [Pb(Mg_(1/3) Nb_(2/3))₀.15 Ti₀.60 (Mg_(1/2) W_(1/2))₀.25 O₃ ] is shown by 6.1×10¹¹ ohm·cm in terms of the specific resistivity. Thus, εεoρ=209 meg·ohm·μF (where ε=3900). Even when the percentage of shrinkage varies by 15±5%, the specific resistivity varies by less than ±10% of the values shown just above. In other words, the specific resistivity of the [Pb(Mg_(1/3) Nb_(2/3) )O₃ -PbTiO₃ -Pb(Mg_(1/2) W_(1/2))O₃ ] type composition is not sufficiently high. Japanese Preliminary Publication No. 144610/1980, Fujiwara et al, contemplates an improvement in the insulating resistance of Pb(Mg_(1/3) Nb_(2/3))O₃ -PbTiO₃ -Pb(Mg_(1/2) W_(1/2))O₃ but in this Publication, any composition having a dielectric constant larger than 10,000 is not disclosed.

As described above, a variety of known ceramic compositions are required to have higher specific resistivity and dielectric constant at temperatures of 20° C. and 125° C.

SUMMARY OF THE INVENTION

It is an object of this invention to provide ternary ceramic compositions consisting essentially of Pb(Mg1/2W_(1/2))O₃ -PbTiO₃ -Pb(Ni_(1/3) Nb_(2/3))O₃ capable of being sintered at temperatures of 900° C. to 1050° C. and having high dielectric constants as well as high specific resistivities at 20° C. and 125° C. Thus, the ceramic compositions of this invention have a dielectric constant of 3,060 to 13,400, a dielectric loss of 0.3 to 3.8%, a specific resistivity of 2.0×10¹² to 1.2×10¹³ ohm·cm at 20° C., εεoρof 1,000 to 5,650 meg·ohm·μF, and a specific resistivity of 4.3×10¹⁰ to 2.5×10¹² ohm·cm at 125° C.

Further more, according to this invention, Nb₂ O₅, Ta₂ O₅, Sb₂ O₃ or Pb(Mn_(1/3) Me_(2/3))O₃ (where Me represents one of Nb, Ta and Sb) are added to the ternary composition described above for greatly improving the bend strength of the ceramic composition, the dielectric loss and the specific resistance.

The ceramic composition of this invention is characterized in that the composition is expressed by [Pb(Mg_(1/2) W_(1/2))O₃ ]_(x) [PbTiO₃ ]_(y) [Pb(Ni_(1/3) Nb_(2/3))O₃ ]_(z) where x+y+z=1.00, and its composition range is on lines interconnecting points A, B, C and D and E in a ternary phase diagram of the composition and in an area bounded by these lines, where

A: (x=0.693, y=0.297 z=0.01)

B: (x=0.495, y=0.495, z=0.01)

C: (x=0.195, y=0.455, z=0.35)

D: (x=0.10, y=0.40, z=0.50)

E: (x=0.06, y=0.24, z=0.70).

Another feature of this invention lies in that oxide of at least one of Nb, Ta and Sb is added to the basic composition described above in 0.02 to 3.0% in terms of atomic percentage of metal element.

Further, according to another modification Pb(Mn_(1/3) Nb_(2/3))O₃, Pb(Mn_(1/3) Ta_(2/3))O₃ or Pb(Mn_(1/3) Sb_(2/3))O₃ is added to the aforementioned basic composition in amounts of 0.05 to 10 mol%, 0.05 to 8 mol% and 0.05 to 6 mol%, respectively.

BRIEF DESCRIPTION OF THE DRAWING

In the accompanying drawing, a single FIGURE shows a ternary phase diagram of a basic ternary ceramic composition embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

To have better understanding of this invention the following examples are given.

EXAMPLE 1

As starting raw materials, were used lead oxide (PbO), magnesium oxide MgO,tungsten oxide WO₃, titanium oxide TiO₂, nickel oxide NiO, and niobium oxide Nb₂ O₅, each having a purity of more than 99.9%, and these raw materials were weighed to have weights as shown in the following Table I. Then the weighed materials were wet admixed in a ball mill, calcinced at 750° to 800° C. and then pulverized with the ball mill. After filteration and drying, an organic binder was put into the powder and pressed into 4 circular discs each having a diameter of 16 mm and a thickness of about 2 mm. The samples falling within the composition range defined by this invention were sintered in air at a temperature of 900° to 1050° C. for one hour. Silver electrodes were bonded to the opposite surfaces of each sintered disc at atemperature of 600° C. The dielectric constant loss and capacitance were measured with a digital LCR meter at a frequency of 1 KHz, voltage of1 V_(rms), and at a temperature of 20° C. to calculate the dielectric constant. The insulating resistances at 20° C. and 125° C. were measured with a ultra high insulating resistance meterwhile applying voltage of 50 V for 1 minute to calculate the specific resistivity. The characteristics of a sample of a particular composition were determined by averaging the test data for four samples.

The ratio of ingredients, dielectric loss, and the specific resistivity at 20° C. and 125° C. are shown in the following Table I.

                                      TABLE I                                      __________________________________________________________________________                                    Specific                                                                             Specific                                  Ratio of ternary               resisti-                                                                             resisti-                                  ingredients (mol %)            vity at                                                                              vity at                                   Sample                                                                             Pb(Mg1/2  Pb(Ni1/3                                                                            Dielectric                                                                           Dielectric                                                                           20° C.                                                                        125° C.                            No. W1/2)O.sub.3                                                                        PbTiO.sub.3                                                                         Nb2/3)O.sub.3                                                                       constant                                                                             loss (%)                                                                             (Ω · cm)                                                              (Ω · cm)                   __________________________________________________________________________      1* 40   10   50    420  0.1   8.3 × 10.sup.12                                                                2.7 × 10.sup.11                      2  69.3 29.7  1   3060  2.0   9.5 × 10.sup.12                                                                2.5 × 10.sup.12                      3* 60   40   --   3990  1.3   9.3 × 10.sup.11                                                                8.2 × 10.sup.9                       4  57   38    5   6030  2.4   8.1 × 10.sup.12                                                                1.1 × 10.sup.12                      5  51   34   15   5320  0.8   1.2 × 10.sup.13                                                                1.6 × 10.sup.12                      6  49.5 49.5  1   4530  1.8   2.5 × 10.sup.12                                                                3.4 × 10.sup.11                      7  45   45   10   9230  3.7   5.6 × 10.sup.12                                                                6.3 × 10.sup.11                      8  40   40   20   7920  1.8   6.1 × 10.sup.12                                                                1.0 × 10.sup.12                      9  35   35   30   6790  1.0   8.2 × 10.sup.12                                                                6.8 × 10.sup.11                     10  28   42   30   7670  2.8   2.0 × 10.sup.12                                                                7.5 × 10.sup.11                     11  24   36   40   10530 1.8   5.5 × 10.sup.12                                                                4.3 × 10.sup.11                     12  20   30   50   7980  0.5   6.8 × 10.sup.12                                                                1.7 × 10.sup.11                     13  19.5 45.5 35   3450  2.2   4.2 × 10.sup.12                                                                8.3 × 10.sup.11                     14  16.5 38.5 45   7200  2.4   3.7 × 10.sup.12                                                                3.8 × 10.sup.11                     15  13.5 31.5 55   11880 1.9   4.1 × 10.sup.12                                                                1.5 × 10.sup.11                      16*                                                                               16   64   20   1030  2.5   1.3 × 10.sup.12                                                                7.3 × 10.sup.11                     17  10   40   50   5620  2.3   4.5 × 10.sup.12                                                                1.2 × 10.sup.11                     18  8    32   60   13400 3.2   3.2 × 10.sup.12                                                                8.2 × 10.sup.10                     19  6    24   70   9250  0.3   2.8 ×  10.sup.12                                                               4.3 × 10.sup.10                      20*                                                                               4    36   60   14500 0.8   6.5 × 10.sup.11                                                                4.5 × 10.sup.9                      __________________________________________________________________________     Remarks:                                                                       Samples marked with symbol * are not included in the scope of this              invention.                                                               

As can be noted from Table I, the ternary compositions expessed by

    Pb(Mg1/2W1/2)O.sub.3 -PbTiO.sub.2 -Pb(Ni1/3Nb2/3)O.sub.3

and included in the scope of this invention have a high dielectric constantof 3060 to 13,400, small dielectric loss of 0.1 to 3.8%, a high specific resistivity of 2.0×10¹² to 1.2×10¹³ ohm cm at 20° C. and 4.3×10¹⁰ to 2.5×10¹² ohm cm at 125° C. Thus, these compositions are excellent ceramic compositions. Since the ceramic compositions of this invention manifestingthese excellent characteristics can be sintered at a low temperature below 1050° C., not only the internal electrodes in the laminated capacitors can be made of low cost materials but also sintering energy andthe material of the sintering furnace can be saved.

When the ternary compositions of this invention are expressed by [Pb(Mg1/2W1/2)O₃ ]x[PbTiO₃ ]y[Pb(Ni1/3Nb2/3)O₃ ]z (where x+y+z=1.00) their compositions should be on lines interconnecting the following five points of the ternary phase diagram and in an area bounded by these lines as shown in the accompanying drawing.

(x=0.693, y=0.297, z=B 0.01)

(x=0.495, y=0.495, z=0.01)

(x=0.195, y=0.455, z=0.35)

(x=0.10, y=0.40, z=0.50)

(x=0.06, y=0.24, z=0.70).

In the phase diagram, in regions outside the lines interconnecting points 2, 6 and 17, 19, the specific resistivity of the compositions at high temperatures is small. The Curie point of the compositions on the outside of the lines 6, 13 and 17 shifts toward high temperature side from practical range so that their dielectric constant becomes small, whereas on the outside of a line interconnecting points 19 and 2, Curie point shifts toward the low temperature side from the practical range, thereby decreasing the dielectric constant.

In the accompanying drawing, numerals designate the sample numbers shown inTable I.

EXAMPLE 2

In this example, to the ternary composition described above is added 0.02 to 3 atomic % of at least one auxiliary ingredient selected from Nb, Ta and Sb for the purpose of improving the mechanical strength.

In this example, lead oxide PbO, magnesium oxide MgO, tungsten oxide WO₃, titanium oxide TiO₂, nickel oxide NiO, niobium oxide Nb₂ O₅, tantalum oxide Ta₂ O₅ and antimony oxide Sb₂ O₃ each having a purity of higher than 99.9%, were weighed to have a ratio of admixing as shown in Table II. After wet admixing the powders of the raw materials in a ball mill, the mixture was calcined at atemperature of 750° to 800° C., and then pulverized with the ball mill. After filtration and drying, an organic binder was put into thepowder and pressed to obtain 4 circular discs each having a diameter of 16 mm and a thickness of about 2 mm. Further, a cylinder having a diameter of16 mm and a height of 10 mm was formed.

The composition of this example was sintered in air for one hour at a temperature of 900° to 1050° C. Silver electrodes were bounded to the opposite surfaces of each disc and its capacitance and dielectric constant were measured at a frequency of 1 KHz, voltage of 1 Vr.m.s and at a temperature of 20° C. with a digital LCR meter to calculate the dielectric constant.

Then the insulating resistances at 20° C. and 125° C. were measured with a ultra insulating resistance meter in which a voltage of 50V was applied for one minute for calculating the specific resistivity.

For the purpose of evaluating mechanical strength in terms of the bend strength, 10 rectangular pieces each having a thickness of 0.5 mm, a widthof 2 mm and a length of about 13 mm were cut out from the sintered cylinder. A fracture load Pm (Kg) was measured by using two fulcrums spaced 9 mm and the bend strength τ(Kg/cm²) was calculated according to an equation ##EQU1##where l represents the spacing between fulcrums, t the thickness of the sample, and ω the width of the sample. The electric characteristics were determined from a mean value of 4 discs, while the bend strength weredetermined from an average value of 10 rectangular samples.

The ratios of ingredients x, y and z of the main compositions [Pb(Mg1/2W1/2)O₃ ]x[PbTiO₃ ]y[Pb(Ni1/3Nb2/3)O₃ ]z, the quantity of addition of the auxiliary compositions, dielectric constant, dielectric loss, the specific resistivity and bend strength at 20° C. and 125° C. are shown in the following Table II.

                                      TABLE II                                     __________________________________________________________________________                                                   Specific                                                                             Specific                                             Quantity of aux-                                                                           Di- Di- resistiv-                                                                            resistiv-                  Sam- Ratio of main ingredients                                                                           iliary ingredients                                                                         electric                                                                           electric                                                                           ity at                                                                               ity                                                                                  Bend                 ple  (mol %)              Additive                                                                            Quantity                                                                              con-                                                                               loss                                                                               20° C.                                                                        125° C.                                                                       strength             No.                                                                               No                                                                               Pb(Mg1/2W1/2)O.sub.3                                                                   PbTiO.sub.3                                                                         Pb(Ni1/2Nb2/3)O.sub.3                                                                  element                                                                             (Atomic %)                                                                            stant                                                                              (%) (Ω ·                                                                  (Ω ·                                                            cm)   (Kg/cm.sup.2)        __________________________________________________________________________      1*                                                                                1                                                                               60      10   50      --   --      420                                                                               0.0 8.3 × 10.sup.12                                                                9.7                                                                            × 10.sup.11                                                                    560                   2*                                                                                2                                                                               69.3    29.7  1      --   --     3060                                                                               2.1 9.5 × 10.sup.12                                                                2.5                                                                                  620mes. 10.sup.1      3 " "       "    "       Nb   0.3    3210                                                                               2.0 1.7 × 10.sup.13                                                                4.5 × 10.sup.                                                            12    1160                  4 " "       "    "       Ta   0.3    3170                                                                               2.3 1.3 × 10.sup.13                                                                3.4                                                                                  1230es. 10.sup.1      5*                                                                                3                                                                               60      40   --      --   --     3990                                                                               3.3 9.3 × 10.sup.11                                                                8.2 × 10.sup.9                                                                 600                   6*                                                                                4                                                                               57      38    5      --   --     6030                                                                               2.4 8.1 × 10.sup.12                                                                1.1                                                                                  630mes. 10.sup.1      7 " "       "    "       Nb   0.1    6150                                                                               2.5 9.3 × 10.sup.12                                                                1.7                                                                                  1190es. 10.sup.1      8 " "       "    "       "    0.5    6390                                                                               2.8 9.7 × 10.sup.12                                                                2.0                                                                                  1280es. 10.sup.1      9 " "       "    "       Sb   "      6310                                                                               2.7 9.5 × 10.sup.12                                                                1.3                                                                                  1360es. 10.sup.1     10*                                                                                5                                                                               51      34   15      --   --     5320                                                                               0.8 1.2 × 10.sup.12                                                                1.6                                                                                  650mes. 10.sup.1     11 " "       "    "       Nb    0.02  5350                                                                               0.8 1.3 × 10.sup.13                                                                1.6 ×                                                                    10.sup.12                                                                            1050                 12 " "       "    "       "    0.5    5810                                                                               1.2 2.5 × 10.sup.13                                                                3.8                                                                                  1410es. 10.sup.1     13 " "       "    "       "    3.0    5730                                                                               1.4 2.7 × 10.sup.13                                                                4.2                                                                                  1010es. 10.sup.1     14 " "       "    "       Ta    0.02  5380                                                                               0.8 1.2 × 10.sup.13                                                                1.7                                                                                  1000es. 10.sup.1     15 " "       "    "       "    0.5    5870                                                                               1.3 2.1 × 10.sup.13                                                                3.0                                                                                  1310es. 10.sup.1     16 " "       "    "       "    3.0    5650                                                                               1.6 2.5 × 10.sup.13                                                                3.7                                                                                  1070es.10.sup.12     17*                                                                                6                                                                               49.5    49.5  1      --   --     4530                                                                               3.8 2.5 × 10.sup.12                                                                3.4                                                                                  590mes. 10.sup.1     18 " "       "    "       Sb   0.3    4850                                                                               4.1 4.1 × 10.sup.12                                                                5.6                                                                                  1260es. 10.sup.1     19 " "       "    "       Ta   0.3    4780                                                                               3.9 3.7 × 10.sup.12                                                                5.4                                                                                  1320es. 10.sup.1     20*                                                                                7                                                                               45      45   10      --   --     9230                                                                               3.7 5.6 × 10.sup.12                                                                6.3                                                                                  630mes. 10.sup.1     21 " "       "    "       Nb   0.1    9420                                                                               4.2 7.8 × 10.sup.12                                                                8.8                                                                                  1150es. 10.sup.1     22 " "       "    "       Nb   0.5    9570                                                                               4.5 8.6 × 10.sup.12                                                                1.0                                                                                  1330es. 10.sup.1     23 " "       "    "       Ta   0.5    9610                                                                               4.6 8.1 × 10.sup.12                                                                9.6                                                                                  1380es. 10.sup.1     24*                                                                                8                                                                               40      40   20      --   --     7920                                                                               1.8 6.1 × 10.sup.12                                                                1.0                                                                                  610mes. 10.sup.1     25 " "       "    "       Nb     0.02 8050                                                                               1.7 6.4 × 10.sup.12                                                                1.0                                                                                  990mes. 10.sup.1     26 " "       "    "       "    0.5    8310                                                                               2.0 8.7 × 10.sup.12                                                                1.6                                                                                  1310es. 10.sup.1     27 " "       "    "       "    1.0    8360                                                                               2.2 9.2 × 10.sup.12                                                                1.7                                                                                  1150es. 10.sup.1     28 " "       "    "       "    3.0    8230                                                                               2.4 9.5 × 10.sup.12                                                                1.8                                                                                  1060es. 10.sup.1     29*                                                                               " "       "    "       "    5.0    8120                                                                               3.7 7.9 × 10.sup.12                                                                1.3                                                                                  630mes. 10.sup.1     30 " "       "    "       Sb     0.02 7970                                                                               1.8 6.7 × 10.sup.12                                                                1.1                                                                                  1070es. 10.sup.1     31 " "       "    "       Sb   0.5    8270                                                                               2.1 9.1 × 10.sup.12                                                                1.7                                                                                  1360es. 10.sup.1     32 " "       "    "       Ta   0.5    8330                                                                               2.0 8.3 × 10.sup.12                                                                1.3                                                                                  1320es. 10.sup.1     33 " "       "    "       Ta   3.0    8290                                                                               2.6 8.7 × 10.sup.12                                                                1.5                                                                                  1010es. 10.sup.1     34*                                                                                9                                                                               35      35   30      --   --     6790                                                                               1.0 8.2 × 10.sup.12                                                                6.8                                                                                  580mes. 10.sup.1     35 " "       "    "       Sb   0.1    6930                                                                               1.3 9.5 × 10.sup.12                                                                8.1                                                                                  1190es. 10.sup.1     36 " "       "    "       "    1.0    7250                                                                               1.5 1.4 × 10.sup.13                                                                1.1                                                                                  1130es. 10.sup.1     37 " "       "    "       Ta   0.1    6890                                                                               1.2 9.8 × 10.sup.12                                                                8.7                                                                                  1210es. 10.sup.1     38 " "       "    "       "    1.0    7130                                                                               1.5 1.7 × 10.sup.13                                                                1.5                                                                                  1150es. 10.sup.1     39*                                                                               10                                                                               23      42   30      --   --     7670                                                                               2.8 2.0 × 10.sup.12                                                                7.5                                                                                  600mes. 10.sup.1     40 " "       "    "       Nb   0.1    7830                                                                               3.2 2.7 × 10.sup.12                                                                1.0                                                                                  1150es. 10.sup.1     41 " "       "    "       "    0.5    8020                                                                               3.4 3.2 × 10.sup.12                                                                1.3                                                                                  1320es. 10.sup.1     42 " "       "    "       Sb   0.5    7980                                                                               3.3 2.9 × 10.sup.12                                                                1.2                                                                                  1410es. 10.sup.1     43 " "       "    "       "    1.0    8150                                                                               3.7 3.7 × 10.sup.12                                                                1.6                                                                                  1100es. 10.sup.1     44*                                                                               11                                                                               24      36   40      --   --     10530                                                                              1.8 5.5 × 10.sup.12                                                                4.3                                                                                  570mes. 10.sup.1     45 " "       "    "       Nb     0.02 10650                                                                              1.8 5.7 × 10.sup.12                                                                4.3                                                                                  1010es. 10.sup.1     46 " "       "    "            0.1    11280                                                                              2.0 6.8 × 10.sup.12                                                                5.2                                                                                  1130es. 10.sup.1     47 " "       "    "            0.5    11720                                                                              2.2 7.3 × 10.sup.12                                                                5.9                                                                                  1320es. 10.sup.1     48 " "       "    "            1.0    12100                                                                              2.5 8.6 × 10.sup.12                                                                7.2                                                                                  1160es. 10.sup.1     49 " "       "    "       Nb   3.0    11950                                                                              2.7 9.1 × 10.sup.12                                                                7.5                                                                                  1050es. 10.sup.1     50*                                                                               " "       "    "       "    5.0    11050                                                                              3.9 6.1 × 10.sup.12                                                                4.8                                                                                  690mes. 10.sup.1     51 " "       "    "       Sb   0.1    10970                                                                              1.9 7.1 × 10.sup.12                                                                5.2                                                                                  1260es. 10.sup.1     52 " "       "    "       "    1.0    11820                                                                              2.4 8.9 × 10.sup.12                                                                7.1                                                                                  1140es. 10.sup.1     53 " "       "    "       "    3.0    11280                                                                              2.8 9.7 × 10.sup.12                                                                8.1                                                                                  1020es. 10.sup.1     54 " "       "    "       Nb   0.1    11320                                                                              2.1 6.8 × 10.sup.12                                                                5.1                                                                                  1310es. 10.sup.1                               Sb   0.1                                                                       Sb   0.1                                             55 11                                                                               24      36   40      Ta   0.1    11060                                                                              2.0 7.5 × 10.sup.12                                                                5.7                                                                                  1270es. 10.sup.1     56*                                                                               12                                                                               20      30   50      --   0.5    7980                                                                               0.5 6.8 × 10.sup.12                                                                1.7                                                                                  630mes. 10.sup.1     57 " "       "    "       Nb   0.1    8150                                                                               0.8 7.5 × 10.sup.12                                                                2.1                                                                                  1120es. 10.sup.1     58 " "       "    "       "    0.5    8320                                                                               1.0 8.7 × 10.sup.12                                                                2.4                                                                                  1350es. 10.sup.1     59 " "       "    "       Ta   0.5    8280                                                                               0.9 9.1 × 10.sup.12                                                                2.7                                                                                  1380es. 10.sup.1     60*                                                                               13                                                                               19.5    45.5 35      --   --     3450                                                                               2.2 4.2 × 10.sup.12                                                                8.3                                                                                  570mes. 10.sup.1     61 " "       "    "       Nb   0.5    3720                                                                               2.5 6.7 × 10.sup.12                                                                1.3                                                                                  1290es. 10.sup.1     62 " "       "    "       Sb   0.5    3750                                                                               2.7 6.1 × 10.sup.12                                                                1.2                                                                                  1320es. 10.sup.1     63*                                                                               14                                                                               16.5    38.5 45      --   --     7200                                                                               2.4 3.7 × 10.sup.12                                                                3.8                                                                                  610mes. 10.sup.1     64 " "       "    "       Nb   0.1    7830                                                                               2.6 5.3 × 10.sup.12                                                                5.4                                                                                  1180es. 10.sup.1     65 " "       "    "       Nb   1.0    8750                                                                               2.9 6.5 × 10.sup.12                                                                7.3                                                                                  1120es. 10.sup.1     66*                                                                               15                                                                               13.5    31.5 55      --   --     11880                                                                              1.9 4.1 × 10.sup.12                                                                1.5                                                                                  650mes. 10.sup.1     67 " "       "    "       Nb     0.02 11950                                                                              2.0 4.2 × 10.sup.12                                                                1.5                                                                                  1050es. 10.sup.1     68 " "       "    "       "    0.5    13210                                                                              2.3 6.5 × 10.sup.12                                                                2.4                                                                                  1380es. 10.sup.1     69 " "       "    "       "    3.0    12870                                                                              3.5 7.1 × 10.sup.12                                                                2.7                                                                                  1020es. 10.sup.1     70 " "       "    "       Ta   0.5    13090                                                                              2.2 6.8 × 10.sup.12                                                                2.6                                                                                  1350es. 10.sup.1     71*                                                                               16                                                                               16      64   20      --   --     1030                                                                               2.5 1.3 × 10.sup.12                                                                7.3                                                                                  540mes. 10.sup.1     72*                                                                               17                                                                               10      40   50      --   --     5620                                                                               2.3 4.5 × 10.sup.12                                                                1.2                                                                                  620mes. 10.sup.1     73 " "       "    "       Sb   0.5    5950                                                                               2.7 5.9 × 10.sup.12                                                                1.7                                                                                  1280es. 10.sup.1     74 " "       "    "       Ta   0.5    5870                                                                               2.6 6.1 × 10.sup.12                                                                1.8                                                                                  1330es. 10.sup.1     75*                                                                               18                                                                               8       32   60      --   --     13400                                                                              3.2 3.2 × 10.sup.12                                                                8.2                                                                                  650mes. 10.sup.1     76 " "       "    "       Nb   0.3    15120                                                                              3.8 5.2 × 10.sup.12                                                                1.2                                                                                  1230es. 10.sup.1     77 " "       "    "       Sb   0.3    14870                                                                              3.9 5.8 × 10.sup.12                                                                1.3 ×                                                                    10.sup.11                                                                            1310                 78*                                                                               19                                                                               6       24   70      --   --     9250                                                                               0.3 2.8 × 10.sup.12                                                                4.3                                                                                  610mes. 10.sup.1     79 " "       "    "       Nb   0.3    9570                                                                               0.5 4.7 × 10.sup.12                                                                6.1                                                                                  1320es. 10.sup.1     80 " "       "    "       Ta   0.3    9610                                                                               0.7 4.1 × 10.sup.12                                                                5.8                                                                                  1290es. 10.sup.1     81*                                                                               20                                                                               4       36   60      --   --     14500                                                                              0.8 6.5 × 10.sup.11                                                                4.5 × 10.sup.9                                                                 590                  __________________________________________________________________________     Remarks:                                                                       Samples marked with symbol * are basic compositions.                      

As can be noted from this table, the ternary ceramic composition of this invention consisting of the Pb(Mg1/2W1/2)O₃ -PbTiO₃ -Pb(Ni1/3Nb2/3)O₃ and added with at least one auxiliary constituent element selected from the group consisting of Nb, Ta and Sb has a high dielectric constant of 3170 to 15120, a small dielectric loss of only 0.5 to 4.6%, a high specific resistivity of 2.7×10¹² to 2.7×10¹³ at 20° C. and 5.8×10¹⁰ to 3.5×10¹² ohm cm even at 125° C., and a sufficiently highbend strength of 990 to 1410 Kg/cm², which means that the ceramic composition of this invention has high reliability and utility.

Since this example also has a low sintering temperature of less than 1050° C., the internal electrodes of the laminated capacitor can bemade of low cost materials.

The quantity of addition of the auxiliary constituent element is limited to0.02 to 3 atomic percent based on the main composition. In regions on the outside of lines interconnection points 2 and 6 and points 17 and 19, the specific resistivity of the compositions at high temperatures is small. The Curie point of the compositions on the outside of the lines 6, 13 and 17 shifts toward high temperature side from practical range so that their dielectric constant becomes small, whereas on the outside of a line interconnecting points 19 and 2, Curie point shifts toward the low temperature side from the practical range, thereby decreasing the dielectric constant.

When the quantity of one or more of the auxiliary ingradients Nb, Ta and Sbis less than 0.02 atomic %, the bend strength can not be improved as desired, whereas when this quantity exceeds 3 atomic %, the bend strength decreases.

EXAMPLE 3

In this example, 0.05 to 8 mol % of lead manganese tantalate Pb (Mn1/3Ta2/3)O₃ is used as the auxiliary component for the purpose of improving the mechanical strength of the ceramic composition of Example 1.

More particularly, lead oxide (PbO) magnesium oxide (MgO), tungsten oxide WO₃, titanium oxide (TiO₂), nickel oxide NiO, niobium oxide (Nb₂ O₅), tantalum oxide (Ta₂ O₅) and manganese carbonate (MnCO₃), each having a purity of higher than 99.9%, were used as raw materials and weighed to form a ratio of ingredients as shown in the following Table III. The weighed raw materials were wet admixed in a ball mill and calcined at a temperature of 750° to 800° C.The calcined mixture was pulverized with a ball mill. After filtration and drying, an organic binder was put inyo the powder and pressed into 4 circular discs each having a diameter of 16 mm and a thickness of about 2 mm and into a cylinder having a diameter of 16 mm and a thickness of 10 mmin the same manner as in Example 2. These samples were then sintered in airat a temperature of 900° to 1050° C. Silver electrodes were bonded to the opposite surfaces of each sintered disc and the dielectric constant was calculated by measuring the dielectric loss under the same conditions and with the same meter as in Examples 1 and 2. Then, the insulating resistance was measured by applying 50 V for one minute at temperatures of 20° C. and 125° C. to calculate the specificresistivity.

The mechanical strength was measured by measuring the bend strength just inthe same manner as in Example 2, and the electrical characteristics were also determined in the same manner as in Example 2.

The ratios of ingredients x, y, z of the main ceramic composition [Pb(Mg1/2W1/2)O₃ ]x[PbTiO₃ ]y[Pb(Ni1/3Nb2/3)O₃ ]z, the quantity of the auxiliary components, dielectric constant, dielectric loss, the specific resistivity at 20° C. and 125° C., and the bend strength are shown in the following Table III.

                                      TABLE III                                    __________________________________________________________________________                               Additive quan-      Specific                                                                             Specific                                             tity of aux-        resistiv-                                                                            resistiv-                  Sam-                                                                              Ratio of main ingredients                                                                             iliary ingredi-     ity at                                                                               ity                                                                                  Bend                 ple                                                                               (mol %)                ents (mol %)                                                                           Dielectric                                                                           Dielectric                                                                           20° C.                                                                        125° C.                                                                       strength             No.                                                                               No                                                                               Pb(Mg1/2W1/2)O.sub.3                                                                   PbTiO.sub.3                                                                         Pb(Ni1/2 Nb2/3 )O.sub.3                                                                Pb(Mn1/3Ta2/3)O.sub.3                                                                  constant                                                                             loss (%)                                                                             (Ω ·                                                                  (Ω ·                                                            cm)   (Kg/cm.sup.2)        __________________________________________________________________________      1*                                                                                1                                                                               40      10   50      --       420  0.1   8.3 × 10.sup.12                                                                9.7                                                                            × 10.sup.11                                                                    560                   2*                                                                                2                                                                               69.3    29.7  1      --      3060  2.0   9.5 × 10.sup.12                                                                2.5                                                                                  620mes. 10.sup.1      3 " "       "    "       2.0     2930  0.6   1.2 × 10.sup.12                                                                3.4                                                                                  1280es. 10.sup.1      4*                                                                                3                                                                               60      40   --      --      3990  3.3   9.3 ×                                                                          8.2 × 10.sup.9                                                                 600                   5*                                                                                4                                                                               57      38    5      --      6030  2.4   8.1 × 10.sup.12                                                                1.1                                                                                  630mes. 10.sup.1      6 " "       "    "       0.1     6060  1.9   8.9 × 10.sup.12                                                                1.2                                                                                  1110es. 10.sup.1      7 " "       "    "       2.0     5860  1.0   9.6 × 10.sup.12                                                                1.4                                                                                  1350es. 10.sup.1      8*                                                                                5                                                                               51      34   15      --      5320  0.8   1.2 × 10.sup.12                                                                1.5                                                                                  650mes. 10.sup.1      9 " "       "    "        0.05   5430  0.7   1.3 × 10.sup.12                                                                1.7                                                                                  1020es. 10.sup.1     10 " "       "    "       0.5     5360  0.5   1.4 × 10.sup.12                                                                1.9                                                                                  1230es. 10.sup.1     11 " "       "    "       5.0     5090  0.5   1.6 × 10.sup.12                                                                2.2                                                                                  1120es. 10.sup.1     12 " "       "    "       10.0    4820  1.1   8.3 × 10.sup.12                                                                1.0                                                                                  1060es. 10.sup.1     13*                                                                                6                                                                               49.5    49.5  1      --      4530  3.8   2.5 × 10.sup.12                                                                3.4                                                                                  590mes. 10.sup.1     14 " "       "    "       2.0     4360  2.4   3.1 × 10.sup.12                                                                4.1                                                                                  1290es. 10.sup.1     15*                                                                                7                                                                               45      45   10      --      9230  3.7   5.6 × 10.sup.12                                                                6.3                                                                                  630mes. 10.sup.1     16 " "       "    "       0.1     9310  3.1   6.1 × 10.sup.12                                                                7.1                                                                                  1080es. 10.sup.1     17 " "       "    "       2.0     8870  2.5   6.7 × 10.sup.12                                                                8.0                                                                                  1380es. 10.sup.1     18*                                                                                8                                                                               40      40   20      --      7920  1.8   6.1 × 10.sup.12                                                                1.0                                                                                  610mes. 10.sup.1     19 " "       "    "        0.05   8130  1.6   6.3 × 10.sup.12                                                                1.1                                                                                  1060es. 10.sup.1     20 " "       "    "       0.5     7990  1.1   6.9 × 10.sup.12                                                                1.3                                                                                  1250es. 10.sup.1     21 " "       "    "       1.0     7850  0.7   7.6 × 10.sup.12                                                                1.4                                                                                  1410es. 10.sup.1     22 " "       "    "       5.0     7580  0.9   7.3 × 10.sup.12                                                                1.2                                                                                  1190es. 10.sup.1     23 " "       "    "       10.0    7120  2.0   4.5 × 10.sup.12                                                                7.1                                                                                  1010es. 10.sup.1     24*                                                                               " "       "    "       15.0    6750  2.7   2.1 × 10.sup.12                                                                4.7                                                                                  690mes. 10.sup.1     25*                                                                                9                                                                               35      35   30      --      6790  1.0   8.2 × 10.sup.12                                                                6.8                                                                                  580mes. 10.sup.1     26 " "       "    "       0.1     6850  0.8   8.4 × 10.sup.12                                                                6.9                                                                                  1090es. 10.sup.1     27 " "       "    "       2.0     6530  0.6   9.7 × 10.sup.12                                                                8.8                                                                                  1280es. 10.sup.1     28*                                                                               10                                                                               28      42   30      --      7670  2.8   2.0 × 10.sup.12                                                                7.5                                                                                  600mes. 10.sup.1     29 " "       "    "       0.1     7730  2.3   2.1 × 10.sup.12                                                                7.8                                                                                  1130es. 10.sup.1     30 " "       "    "       2.0     7350  1.6   2.9 × 10.sup.12                                                                1.1 ×                                                                    10.sup.12                                                                            1350                 31*                                                                               11                                                                               24      36   40      --      10530 1.8   5.5 × 10.sup.12                                                                4.3                                                                                  570mes. 10.sup.1     32 " "       "    "        0.05   10830 1.7   5.8 × 10.sup.12                                                                4.9                                                                                  990mes. 10.sup.1     33 " "       "    "       0.5     10620 1.3   6.1 × 10.sup.12                                                                5.3                                                                                  1200es. 10.sup.1     34 " "       "    "       1.0     10460 0.8   6.8 × 10.sup.12                                                                6.3                                                                                  1360es. 10.sup.1     35 " "       "    "       5.0     10090 1.0   6.3 × 10.sup.12                                                                5.8                                                                                  1130es. 10.sup.1     36 " "       "    "       10.0    9480  2.2   4.1 × 10.sup.12                                                                3.0                                                                                  1030es. 10.sup.1     37*                                                                               " "       "    "       15.0    8950  2.8   1.7 × 10.sup.12                                                                1.5                                                                                  610mes. 10.sup.1     38*                                                                               12                                                                               20      30   50      --      7980  0.5   6.8 × 10.sup.12                                                                1.7                                                                                  630mes. 10.sup.1     39 " "       "    "       0.1     8040  0.4   7.3 × 10.sup.12                                                                1.8                                                                                  1080es. 10.sup.1     40 " "       "    "       2.0     7710  0.3   7.8 × 10.sup.12                                                                2.5                                                                                  1430es. 10.sup.1     41*                                                                               13                                                                               19.5    45.5 35      --      3450  2.2   4.2 × 10.sup.12                                                                8.3                                                                                  570mes. 10.sup.1     42 " "       "    "       2.0     3370  1.3   5.7 × 10.sup.12                                                                1.3                                                                                  1250es. 10.sup.1     43*                                                                               14                                                                               16.5    38.5 45      --      7200  2.4   3.7 × 10.sup.12                                                                3.8                                                                                  610mes. 10.sup.1     44 " "       "    "       2.0     7030  1.6   4.5 × 10.sup.12                                                                4.9                                                                                  1360es. 10.sup.1     45*                                                                               15                                                                               13.5    31.5 55      --      11880 1.9   4.1 × 10.sup.12                                                                1.5                                                                                  650mes. 10.sup.1     46 " "       "    "        0.05   12270 1.7   4.3 × 10.sup.12                                                                1.7                                                                                  1050es. 10.sup.1     47 " "       "    "       0.5     12010 1.4   5.7 × 10.sup.12                                                                2.3                                                                                  1280es. 10.sup.1     48 " "       "    "       5.0     11330 1.2   5.1 × 10.sup.12                                                                2.2                                                                                  1210es. 10.sup.1     49 " "       "    "       10.0    10510 2.4   2.8 × 10.sup.12                                                                9.5                                                                                  1030es. 10.sup.1     50*                                                                               16                                                                               16      64   20      --      1030  2.5   1.3 × 10.sup.12                                                                7.3                                                                                  540mes. 10.sup.1     51*                                                                               17                                                                               10      40   50      --      5620  2.3   4.5 × 10.sup.12                                                                1.2                                                                                  620mes. 10.sup.1     52 " "       "    "       2.0     5410  1.6   5.8 × 10.sup.12                                                                2.0                                                                                  1310es. 10.sup.1     53*                                                                               18                                                                               8       32   60      --      13400 3.2   3.2 × 10.sup.12                                                                8.2                                                                                  650mes. 10.sup.1     54 " "       "    "       2.0     13060 2.4   4.7 × 10.sup.12                                                                1.3                                                                                  1330es. 10.sup.1     55*                                                                               19                                                                               6       24   70      --      9250  0.3   2.8 × 10.sup.12                                                                4.3                                                                                  610mes. 10.sup.1     56 " "       "    "       2.0     8920  0.2   4.2 × 10.sup.12                                                                8.3                                                                                  1280es. 10.sup.1     57*                                                                               20                                                                               4       36   60      --      14500 0.8   6.5 ×                                                                          4.5 × 10.sup.9                                                                 590                  __________________________________________________________________________     Remarks:                                                                       Samples marked with symbol * are basic compositions.                      

As can be noted from this Table, the ternary ceramic composition of this example consisting of Pb(Mg1/2W1/2)O₃ -PbTiO₃ -Pb(Ni1/3Nb2/3)O₃ and Pb(Mn1/3Ta2/3)O₃ has a high dielectric constant of 3090 to 13510, a small dielectric loss of 0.3 to 3.1%, a high specific resistivity of 3.5×10¹² to 2.1×10¹³ ohm cm,and a sufficiently high bend strength of 980 to 1410 Kg/cm². The low sintering temperature of less than 1050° C. also results in the same advantageous results as in the foregoing Examples.

The quantity of the auxiliary component Pb(Mn1/3Ta2/3)O₃ should be limited in a range of 0.05 to 8 mol % because, the regions on the outside of lines interconnecting points 2 and 6, and 17 and 19, the specific resistivity decreases at high temperatures. Further, in regions on the outside of lines interconnecting points 6, 13 and 17 the Curie point shifts greatly toward the high temperature side, thus reducing the dielectric constant, whereas in a region on the outside of a line interconnecting points 19 and 2, the Curie point shifts toward the low temperature side, thus reducing the dielectric constant.

When the quantity of addition of the auxiliary composition Pb(Mn1/3Ta2/3)O₃ is less than 0.05 mol %, the bend strength can not be improved as desired, whereas with a quantity exceeding 8 mol %, the bend strength decreases.

EXAMPLE 4

In this example, 0.05 to 10 mol % of lead manganese niobate [Pb(Mn1/3Nb2/3)O₃ ] was added to the ternary composition of Example 1as the auxiliary ingredient for the purpose of improving the mechanical strength.

More particularly, powders of lead oxide PbO, magnesium oxide MgO, tungstenoxide WO₃, titanium oxide TiO₂, nickel oxide NiO, niobium oxide Nb₂ O₅, and manganese carbonate MnCO₃, each having a purityof higher than 99.9%, where weighed to form a ratio of ingredients as shownin the following Table IV, the weighed materials were wet admixed with a ball mill, then calcined at a temperature of 750° to 800° C.Then the calcined mixture was pulverized with a ball mill. After filtrationand drying, an organic binder was put into the powder and pressed into 4 circular discs each having a diameter of 16 mm and a thickness of about 2 mm and into a cylinder having a diameter of 16 mm and a height of about 10mm. These samples were sintered in air at a temperature of 900° to 1050° C. for one hour. The dielectric constant, the mechanical strength, and the specific resistivity at 20° C. and 125° C. were measured just in the same manner as in Examples 2 and 3. The ratios of ingredients x, y and z of the main ternary ceramic composition [Pb(Mg1/2W1/2)O₃ ]x[PbTiO₃ ]y[Pb(Ni1/3Nb2/3)O₃ ]z, the quantity of the auxiliary composition, dielectric constant, dielectric loss, specific resistivity at 20° C. and 125° C. and the bend strength are shown in the following Table IV.

                                      TABLE IV                                     __________________________________________________________________________                               Additive quan-      Specific                                                                             Specific                                             tity of aux-        resistv-                                                                             resistiv-                  Sam-                                                                              Ratio of main ingredients                                                                             iliary ingredi-     ity at                                                                               ity                                                                                  Bend                 ple                                                                               (mol %)                ents (mol %)                                                                           Dielectric                                                                           Dielectric                                                                           20° C.                                                                        125° C.                                                                       strength             No.                                                                               No                                                                               Pb(Mg1/2W1/2)O.sub.3                                                                   PbTiO.sub.3                                                                         Pb(Ni1/2Nb2/3 )O.sub.3                                                                 Pb(Mn1/3Nb2/3)O.sub.3                                                                  constant                                                                             loss (%)                                                                             (Ω ·                                                                  (Ω ·                                                            cm)   (Kg/cm.sup.2)        __________________________________________________________________________      1*                                                                                1                                                                               40      10   50      --       420  0.1   8.3 × 10.sup.12                                                                9.7                                                                            × 10.sup.11                                                                    560                   2*                                                                                2                                                                               69.3    29.7  1      --      3060  2.0   9.5 × 10.sup.12                                                                2.5                                                                                  620mes. 10.sup.1      3 " "       "    "       2.0     2930  0.6   1.2 × 10.sup.12                                                                3.4                                                                                  1280es. 10.sup.1      4*                                                                                3                                                                               60      40   --      --      3990  3.3   9.3 × 10.sup.                                                                  8.2 × 10.sup.9                                                                 600                   5*                                                                                4                                                                               57      38    5      --      6030  2.4   8.1 × 10.sup.12                                                                1.1                                                                                  630mes. 10.sup.1      6 " "       "    "       0.1     6060  1.9   8.9 × 10.sup.12                                                                1.2                                                                                  1110es. 10.sup.1      7 " "       "    "       2.0     5860  1.0   9.6 × 10.sup.12                                                                1.4                                                                                  1350es. 10.sup.1      8*                                                                                5                                                                               51      34   15      --      5320  0.8   1.2 × 10.sup.12                                                                1.6                                                                                  650mes. 10.sup.1      9 " "       "    "        0.05   5430  0.7   1.3 × 10.sup.12                                                                1.7                                                                                  1020es. 10.sup.1     10 " "       "    "       0.5     5360  0.5   1.4 × 10.sup.12                                                                1.9                                                                                  1230es. 10.sup.1     11 " "       "    "       5.0     5090  0.5   1.6 × 10.sup.12                                                                2.2                                                                                  1120es. 10.sup.1     12 " "       "    "       10.0    4820  1.1   8.3 × 10.sup.12                                                                1.0                                                                                  1060es. 10.sup.1     13*                                                                                6                                                                               49.5    49.5  1      --      4530  3.8   2.5 × 10.sup.12                                                                3.4                                                                                  590mes. 10.sup.1     14 " "       "    "       2.0     4360  2.4   3.1 × 10.sup.12                                                                4.1                                                                                  1290es. 10.sup.1     15*                                                                                7                                                                               45      45   10      --      9230  3.7   5.6 × 10.sup.12                                                                6.3                                                                                  630mes. 10.sup.1     16 " "       "    "       0.1     9310  3.1   6.1 × 10.sup.12                                                                7.1                                                                                  1080es. 10.sup.1     17 " "       "    "       2.0     8870  2.5   6.7 × 10.sup.12                                                                8.0                                                                                  1380es. 10.sup.1     18*                                                                                8                                                                               40      40   20      --      7920  1.8   6.1 × 10.sup.12                                                                1.0                                                                                  610mes. 10.sup.1     19 " "       "    "        0.05   8130  1.6   6.3 × 10.sup.12                                                                1.1                                                                                  1060es. 10.sup.1     20 " "       "    "       0.5     7990  1.1   6.9 × 10.sup.12                                                                1.3                                                                                  1250es. 10.sup.1     21 " "       "    "       1.0     7850  0.7   7.6 × 10.sup.12                                                                1.4                                                                                  1410es. 10.sup.1     22 " "       "    "       5.0     7580  0.9   7.3 × 10.sup.12                                                                1.2                                                                                  1190es. 10.sup.1     23 " "       "    "       10.0    7120  2.0   4.5 × 10.sup.12                                                                7.1                                                                                  1010es. 10.sup.1     24*                                                                               " "       "    "       15.0    6750  2.7   2.1 × 10.sup.12                                                                4.7                                                                                  690mes. 10.sup.1     25*                                                                                9                                                                               35      35   30      --      6790  1.0   8.2 × 10.sup.12                                                                6.8                                                                                  580mes. 10.sup.1     26 " "       "    "       0.1     6850  0.8   8.4 × 10.sup.12                                                                6.9                                                                                  1090es. 10.sup.1     27 " "       "    "       2.0     6530  0.6   9.7 × 10.sup.12                                                                8.8                                                                                  1280es. 10.sup.1     28*                                                                               10                                                                               28      42   30      --      7670  2.8   2.0 × 10.sup.12                                                                7.5                                                                                  600mes. 10.sup.1     29 " "       "    "       0.1     7730  2.3   2.1 × 10.sup.12                                                                7.8                                                                                  1130es. 10.sup.1     30 " "       "    "       2.0     7350  1.6   2.9 × 10.sup.12                                                                1.1 ×                                                                    10.sup.12                                                                            1350                 31*                                                                               11                                                                               24      36   40      --      10530 1.8   5.5 × 10.sup.12                                                                4.3                                                                                  570mes. 10.sup.1     32 " "       "    "        0.05   10830 1.7   5.8 × 10.sup.12                                                                4.9                                                                                  990mes. 10.sup.1     33 " "       "    "       0.5     10620 1.3   6.1 × 10.sup.12                                                                5.3                                                                                  1200es. 10.sup.1     34 " "       "    "       1.0     10460 0.3   6.8 × 10.sup.12                                                                6.3                                                                                  1360es. 10.sup.1     35 " "       "    "       5.0     10090 1.0   6.3 × 10.sup.12                                                                5.8                                                                                  1130es. 10.sup.1     36 " "       "    "       10.0    9480  2.2   4.1 × 10.sup.12                                                                3.0                                                                                  1030es. 10.sup.1     37*                                                                               " "       "    "       15.0    8950  2.8   1.7 × 10.sup.12                                                                1.5                                                                                  610mes. 10.sup.1     38*                                                                               12                                                                               20      30   50      --      7980  0.5   6.8 × 10.sup.12                                                                1.7                                                                                  630mes. 10.sup.1     39 " "       "    "       0.1     8040  0.4   7.3 × 10.sup.12                                                                1.8                                                                                  1080es. 10.sup.1     40 " "       "    "       2.0     7710  0.3   7.8 × 10.sup.12                                                                2.5                                                                                  1430es. 10.sup.1     41*                                                                               13                                                                               19.5    45.5 35      --      3450  2.2   4.2 × 10.sup.12                                                                8.3                                                                                  570mes. 10.sup.1     42 " "       "    "       2.0     3370  1.3   5.7 × 10.sup.12                                                                1.3                                                                                  1250es. 10.sup.1     43*                                                                               14                                                                               16.5    38.5 45      --      7200  2.4   3.7 × 10.sup.12                                                                3.8                                                                                  610mes. 10.sup.1     44 " "       "    "       2.0     7030  1.6   4.5 × 10.sup.12                                                                4.9                                                                                  1360es. 10.sup.1     45*                                                                               15                                                                               13.5    31.5 55      --      11880 1.9   4.1 × 10.sup.12                                                                1.5                                                                                  650mes. 10.sup.1     46 " "       "    "        0.05   12270 1.7   4.3 × 10.sup.12                                                                1.7                                                                                  1050es. 10.sup.1     47 " "       "    "       0.5     12010 1.4   5.7 × 10.sup.12                                                                2.3                                                                                  1280es. 10.sup.1     48 " "       "    "       5.0     11330 1.2   5.1 × 10.sup.12                                                                2.2                                                                                  1210es. 10.sup.1     49 " "       "    "       10.0    10510 2.4   2.8 × 10.sup.12                                                                9.5                                                                                  1030es. 10.sup.1     50*                                                                               16                                                                               16      64   20      --      1030  2.5   1.3 × 10.sup.12                                                                7.3                                                                                  540mes. 10.sup.1     51*                                                                               17                                                                               10      40   50      --      5620  2.3   4.5 × 10.sup.12                                                                1.2                                                                                  620mes. 10.sup.1     52 " "       "    "       2.0     5410  1.6   5.8 × 10.sup.12                                                                2.0                                                                                  1310es. 10.sup.1     53*                                                                               18                                                                               8       32   60      --      13400 3.2   3.2 × 10.sup.12                                                                8.2                                                                                  650mes. 10.sup.1     54 " "       "    "       2.0     13060 2.4   4.7 × 10.sup.12                                                                1.3                                                                                  1330es. 10.sup.1     55*                                                                               19                                                                               6       24   70      --      9250  0.3   2.8 × 10.sup.12                                                                4.3                                                                                  610mes. 10.sup.1     56 " "       "    "       2.0     8920  0.2   4.2 × 10.sup.12                                                                8.3                                                                                  1280es. 10.sup.1     57*                                                                               20                                                                               4       36   60      --      14500 0.8   6.5 ×                                                                          4.5 × 10.sup.9                                                                 590                  __________________________________________________________________________     Remarks:                                                                       Samples marked with symbol * are basic compositions.                      

As can be noted from this Table IV, the ternary ceramic composition of thisinvention consisting of Pb(Mg1/2W1/2)O₃ -PbTiO₂ -Pb(Ni1/3Nb2/3)O₃ and Pb(Mn1/3Nb2/3)O₃ has a high dielectric constant of 2930 to 13060, a low dielectric loss of 0.2 to 3.1%, a high specific resistivity of 2.1×10¹² to 1.6×10¹³ ohm. cmat 20° C. and 8.3×10¹⁰ to 3.4×10¹² ohm.cm evenat a high temperature of 125° C., and a high bend strength of 990 to1430 Kg/cm². In this Example, too, since the sintering temperature is below 1050° C., the same advantages as in the foregoing Examples can be realized. The reason for limiting the quantity of the auxiliary component Pb(Mn1/3Nb2/3)O₃ to be in a range of 0.05 to 10 mol % lies in that in regions on the outside of lines interconnecting points 2 and 6and points 17 and 19, the specific resistivity decreases at high temperatures, that in the region on the outside of lines interconnecting points 6, 13 and 17, the Curie point shifts greatly toward the high temperature side, thereby decreasing the dielectric constant, and that in a region on the outside of a line interconnecting points 19 and 2, the Curie point shifts greatly toward the low temperature side, thus decreasing the dielectric constant. Less than 0.05 mol % of Pb(Mn1/3Nb2/3)O₃ can not improve the bend strength as desired whereasmore than 10 mol % of the auxiliary ingredient decreases the bend strength.

EXAMPLE 5

In this Example, 0.05 to 6 mol % of lead manganese antimonate Pb(Mn1/3Sb2/3)O₃ is added to the basic ternary ceramic composition ofExample 1 for the purpose of improving the mechanical strength.

More particularly, in this example, powders of lead oxide PbO, magnesium oxide MgO, tungsten oxide WO₃, titanium oxide TiO₂, nickel oxideNiO, niobium oxide Nb₂ O₅, antimony oxide Sb₂ O₃, and manganese carbonate MnCO₃ were weighed to have a composition ratio asshown in the following Table V. Thereafter, samples in the form of circulardiscs and a cylinder were prepared and sintered in air at a temperature of 900° C. to 1050° C. in the same manner as in Examples 2, 3 and 4, and their dielectric constant, specific resistivity at 20° C. and 125° C., and mechanical strength that is the bend strength were determined in the same manner.

The ratio x, y and z of the main composition [Pb(Mg1/2W1/2)O₃ ]x[PbTiO₃ ]y[Pb(Ni1/3Nb2/3)O₃ ]z, the quantity of the auxiliary component Pb(Mn1/3Sb2/3)O₃, dielectric constant, dielectric loss, specific resistivity at 20° C. and 125° C. and the bend strength are shown in the following Table V.

                                      TABLE V                                      __________________________________________________________________________                               Additive quan-      Specific                                                                             Specific                                             tity of aux-        resistiv-                                                                            resistiv-                  Sam-                                                                              Ratio of main ingredients                                                                             iliary ingredi-     ity at                                                                               ity                                                                                  Bend                 ple                                                                               (mol %)                ents (mol %)                                                                           Dielectric                                                                           Dielectric                                                                           20°                                                                           125°                                                                          strength             No.                                                                               No                                                                               Pb(Mg1/2W1/2)O.sub.3                                                                   PbTiO.sub.3                                                                         Pb(Ni1/2Nb2/3)O.sub.3                                                                  Pb(Mn1/3Sb2/3)O.sub.3                                                                  constant                                                                             loss (%)                                                                             (Ω ·                                                                  (Ω ·                                                            cm)   (Kg/cm.sup.2)        __________________________________________________________________________      1*                                                                                1                                                                               40      10   50      --       420  0.1   8.3 × 10.sup.12                                                                9.7                                                                            × 10.sup.11                                                                    560                   2*                                                                                2                                                                               69.3    29.7  1      --      3060  2.0   9.5 × 10.sup.12                                                                2.5                                                                                  620mes. 10.sup.1      3 " "       "    "       1.0     2950  0.9   1.4 × 10.sup.12                                                                3.8                                                                                  1390es. 10.sup.1      4*                                                                                3                                                                               60      40   --      --      3990  3.3   9.3 × 10.sup.11                                                                8.2 ×  10.sup.9                                                                600                   5*                                                                                4                                                                               57      38    5      --      6030  2.4   8.1 × 10.sup.12                                                                1.1                                                                                  630mes. 10.sup.1      6 " "       "    "       0.1     6180  1.6   9.6 × 10.sup.12                                                                1.4                                                                                  1300es. 10.sup.1      7 " "       "    "       1.0     5790  1.3   9.3 × 10.sup.12                                                                1.3                                                                                  1280es. 10.sup.1      8*                                                                                5                                                                               51      34   15      --      5320  0.8   1.2 × 10.sup.12                                                                1.6                                                                                  650mes. 10.sup.1      9 " "       "    "        0.05   5380  0.7   1.4 × 10.sup.12                                                                1.9                                                                                  1030es. 10.sup.1     10 " "       "    "       0.5     5300  0.6   1.7 × 10.sup.12                                                                2.4                                                                                  1350es. 10.sup.1     11 " "       "    "       3.0     5070  0.6   1.3 × 10.sup.12                                                                1.9                                                                                  1210es. 10.sup.1     12 " "       "    "       6.0     4750  1.3   7.6 × 10.sup.12                                                                9.4                                                                                  1000es. 10.sup.1     13  6                                                                               49.5    49.5  1      --      4530  3.8   2.5 × 10.sup.12                                                                3.4                                                                                  590mes. 10.sup.1     14 " "       "    "       1.0     4460  2.6   3.9 × 10.sup.12                                                                5.9                                                                                  1250es. 10.sup.1     15  7                                                                               45      45   10      --      9230  3.7   5.6 × 10.sup.12                                                                6.3                                                                                  630mes. 10.sup.1     16 " "       "    "       0.1     9350  2.8   7.3 × 10.sup.12                                                                8.8                                                                                  1330es. 10.sup.1     17 " "       "    "       1.0     9080  2.3   6.5 × 10.sup.12                                                                8.2                                                                                  1280es. 10.sup.1     18*                                                                                8                                                                               40      40   20      --      7920  1.8   6.1 × 10.sup.12                                                                1.0                                                                                  610mes. 10.sup.1     19 " "       "    "        0.05   8050  1.5   6.7 × 10.sup.12                                                                1.2                                                                                  1050es. 10.sup.1     20 " "       "    "       0.5     7940  0.9   7.4 × 10.sup.12                                                                1.4                                                                                  1390es. 10.sup.1     21 " "       "    "       1.0     7710  0.7   7.1 × 10.sup.12                                                                1.3                                                                                  1360es. 10.sup.1     22 " "       "    "       3.0     7520  1.2   6.3 × 10.sup.12                                                                1.1                                                                                  1180es. 10.sup.1     23 " "       "    "       6.0     7050  2.4   3.5 × 10.sup.12                                                                6.0                                                                                  1030es. 10.sup.1     24*                                                                               " "       "    "       9.0     6590  3.1   1.6 × 10.sup.12                                                                2.4                                                                                  690mes. 10.sup.1     25*                                                                                9                                                                               35      35   30      --      6790  1.0   8.2 × 10.sup.12                                                                6.8                                                                                  580mes. 10.sup.1     26 " "       "    "       0.1     6910  0.8   1.0 × 10.sup.12                                                                9.2                                                                                  1290es. 10.sup.1     27 " "       "    "       1.0     6600  0.6   9.6 × 10.sup.12                                                                8.8                                                                                  1260es. 10.sup.1     28*                                                                               10                                                                               28      42   "       --      7670  2.8   2.0 × 10.sup.12                                                                7.5                                                                                  600mes. 10.sup.1     29 " "       "    "       0.1     7860  2.1   3.9 × 10.sup.12                                                                1.5                                                                                  1350es. 10.sup.1     30 " 28      "    "       1.0     7490  1.6   3.2 × 10.sup.12                                                                1.2                                                                                  1360es. 10.sup.1     31*                                                                               11                                                                               24      36   40      --      10530 1.8   5.5 × 10.sup.12                                                                4.3                                                                                  570mes. 10.sup.1     32 " "       "    "        0.05   10750 1.6   5.9 × 10.sup.12                                                                5.0                                                                                  980mes. 10.sup.1     33 " "       "    "       0.5     10610 0.9   6.8 × 10.sup.12                                                                5.6                                                                                  1320es. 10.sup.1     34 " "       "    "       1.0     10230 0.8   6.1 × 10.sup.12                                                                5.3                                                                                  1340es. 10.sup.1     35 " "       "    "       3.0     9980  1.4   5.4 × 10.sup.12                                                                4.4                                                                                  1160es. 10.sup.1     36 " "       "    "       6.0     9340  2.5   2.9 × 10.sup.12                                                                3.7                                                                                  1030es. 10.sup.1     37*                                                                               " "       "    "       9.0     8690  3.3   8.7 × 10.sup.11                                                                8.6                                                                                  610mes. 10.sup.1     38*                                                                               12                                                                               20      30   50      0       7980  0.5   6.8 × 10.sup.12                                                                1.7                                                                                  630mes. 10.sup.1     39 " "       "    "       0.1     8030  0.4   8.1 × 10.sup.12                                                                2.6                                                                                  1340es. 10.sup.1     40 " "       "    "       1.0     7710  0.3   7.6 × 10.sup.12                                                                2.3                                                                                  1290es. 10.sup.1     41*                                                                               13                                                                               19.5    45.5 35      --      3450  2.2   4.2 × 10.sup.12                                                                8.3                                                                                  570mes. 10.sup.1     42 " "       "    "       1.0     3380  1.5   5.6 × 10.sup.12                                                                1.2                                                                                  1280es. 10.sup.1     43*                                                                               14                                                                               16.5    38.5 45      --      7200  2.4   3.7 × 10.sup.12                                                                3.8                                                                                  610mes. 10.sup.1     44 " "       "    "       1.0     7040  1.7   4.9 × 10.sup.12                                                                5.7                                                                                  1370es. 10.sup.1     45*                                                                               15                                                                               13.5    31.5 55      --      11880 1.9   4.1 × 10.sup.12                                                                1.5                                                                                  650mes. 10.sup.1     46 " "       "    "        0.05   11930 1.4   4.6 × 10.sup.12                                                                1.8                                                                                  1050es. 10.sup.1     47 " "       "    "       0.5     11950 1.1   6.1 × 10.sup.12                                                                2.6                                                                                  1410es. 10.sup.1     48 " "       "    "       3.0     11230 1.1   3.9 × 10.sup.12                                                                1.5                                                                                  1220es. 10.sup.1     49 " "       "    "       6.0     10560 2.7   1.1 × 10.sup.12                                                                4.0                                                                                  1040es. 10.sup.1     50*                                                                               16                                                                               16      64   20      --      1030  2.5   1.3 × 10.sup.12                                                                7.3                                                                                  540mes. 10.sup.1     51*                                                                               17                                                                               10      40   50      --      5620  2.3   4.5 × 10.sup.12                                                                1.2                                                                                  620mes. 10.sup.1     52 " "       "    "       1.0     5470  1.5   5.8 × 10.sup.12                                                                2.0                                                                                  1320es. 10.sup.1     53*                                                                               18                                                                               8       32   60      --      13400 3.2   3.2 × 10.sup.12                                                                8.2                                                                                  650mes. 10.sup.1     54 " "       "    "       1.0     12960 2.4   4.1 × 10.sup.12                                                                1.3                                                                                  1380es. 10.sup.1     55*                                                                               19                                                                               6       24   70      --      9250  0.3   2.8 × 10.sup.12                                                                4.3                                                                                  610mes. 10.sup.1     56 " "       "    "       1.0     8980  0.3   3.5 × 10.sup.12                                                                6.7                                                                                  1290es. 10.sup.1     57*                                                                               20                                                                               4       36   60      --      14500 0.8   6.5 × 10.sup.11                                                                4.5 × 10.sup.9                                                                 590                  __________________________________________________________________________     Remarks:                                                                       Samples marked with symbol * are basic compositions.                      

As can be noted from this Table V, the ceramic composition of this Example has a high dielectric constant of 2950 to 12960, a low dielectric loss of 0.3 to 2.8%, a high specific resistivity of 1.1×10¹² to 1.7×10¹³ ohm cm at 20° C. and 4.0×10¹⁰ to 3.8×10¹² ohm cm even at a high temperature of 125° C., and a sufficiently high bend strength of 980 to 1410 Kg/cm².

Again the sintering temperature of the Example is below 1050° C.

The reason for limiting the quantity of the auxiliary ingredient to be in the range of 0.05 to 6 mol % lies in that in regions on the outside of lines interconnecting points 2 and 6 and points 17 and 19, the specific resistivity at high temperatures decreases, that in the regions on the outside of lines interconnecting points 6, 13 and 17 the Curie point shifts greatly toward the high temperature side, thereby reducing the dielectric constant, and that in a region on the outside of the points 19 and 2, the Curie point greatly shifts toward the low temperature side, thus decreasing the dielectric constant.

When the quantity of the auxiliary ingredient Pb(Mn1/3Sb2/3)O₃ is lessthan 0.05 mol %, the bend strength can not be improved as desired, whereas when the quantity exceeds beyond 6 mol %, the bend strength decreases. 

What is claimed is:
 1. A ceramic composition consisting essentially of lead magnesium tungstate [Pb(Mg_(1/2) W_(1/2))O₃ ], lead titanate [PbTiO₃ ] and lead nickel niobate [Pb(Ni_(1/3) Nb_(2/3))O₃ ] wherein the composition is expressed by [Pb(Mg_(1/2) W_(1/2))O₃ ]_(x) [PbTiO₃ ]_(y) [Pb(Ni_(1/3) Nb_(2/3))O₃ ]_(z) where x+y+z+1.00, said composition lies on lines interconnecting five points (x=0.693, y=0.297, z=0.01) (x=0.495, y=0.495, z=0.01), (x=0.195, y=0.455, z=0.35), (x=0.10, y=0.40, z=0.50) and (x=0.06, y=0.24, z=0.70) and in a region bounded by said lines.
 2. The ceramic composition according to claim 1 which further comprises 0.02 to 3 atomic % of at least one auxiliary ingredient selected from the group consisting of Nb, Ta and Sb.
 3. The ceramic composition according to claim 1 which further comprises 0.05 to 8 mol % of [Pb(Mn_(1/3) Ta_(2/3))O₃ ].
 4. The ceramic composition according to claim 1 which further comprises 0.05 to 10 mol % of [Pb(Mn_(1/3) Nb_(2/3))O₃ ].
 5. The ceramic composition according to claim 1 which further comprises 0.05 to 6 mol % of [Pb(Mn_(1/3) Sb_(2/3))O₃ ].
 6. The ceramic composition according to claim 1 wherein said composition is sintered at a temperature of 900° to 1050° C. 